1. Field of the Invention
The present invention relates to an electric blower including a diffuser.
2. Description of the Related Art
JP-A 2010-190136, for example, describes an electric blower for use in an electric vacuum cleaner. In this known electric blower, an air flow discharged from a centrifugal impeller rotating at a high speed passes through a diffuser channel portion defined by a plurality of stationary vanes arranged in a spiral pattern, a diffuser base, and an inner wall of a fan case, which gradually increases in a channel area as it approaches an air outlet, and then, the air flow changes its direction to travel in an axial direction toward the air outlet, and passes through an outer channel portion along an inner wall of a housing case. Further, the air flow is guided by return guide vanes arranged below the diffuser to pass through a return channel portion inside the inner wall of the housing case, and is finally discharged out of the electric blower through the air outlet of the housing case.
In the electric blower described in JP-A 2010-190136, the return guide vanes, which together define the return channel portion, are integrally defined with a lower surface of the diffuser, which includes the stationary vanes arranged in the spiral pattern at an outer circumferential portion of the diffuser base.
In the electric blower described above, an air flow travelling radially outward and produced by the centrifugal impeller is guided by the stationary vanes of the diffuser, and is caused by the stationary vanes to change its direction to travel in a circumferential direction. Then, the air flow is turned 180 degrees by the inner wall of the housing case to enter into a space between the housing case and the diffuser. At this time, under the diffuser, the air flow, caused by the inner wall of the housing case to change its direction, travels along the inner surface of the housing case. In the known electric blower, the return guide vanes are integrally defined with the lower surface of the diffuser, and gaps are defined between the return guide vanes and the inner surface of the housing case because of tolerances. Accordingly, a portion of the air flow guided to the space under the diffuser enters into such a gap, so that the air flow is not smoothly guided, and a loss occurs. In addition, noise may occur as a result of air entering into such a gap.